Glass sheet processing method and glass sheet processing apparatus

Abstract

A glass sheet processing method is provided for irradiating a laser beam on a glass sheet and forming a cleavage in the glass sheet with thermal stress. If each of an irradiation area of the laser beam on the surface and an irradiation area of the laser beam on the back face of the glass sheet includes a peak position of a power density of the laser beam, each irradiation area has an asymmetrical power density distribution that is asymmetrical with respect to a reference line that passes through the peak position and is parallel to a moving direction of the peak position. If each irradiation area has no peak position, each irradiation area has an asymmetrical shape that is asymmetrical with respect to a reference line that passes through a centroid position of the irradiation area and is parallel to a moving direction of the centroid position.

What is claimed is: 
     
       1. A glass sheet processing method, comprising:
 irradiating a laser beam on a glass sheet such that the laser beam is transmitted through the glass sheet from a surface to a back face of the glass sheet; 
 moving an irradiating position of the laser beam with respect to the glass sheet; and 
 forming a cleavage in the glass sheet with thermal stress that is generated by irradiating the laser beam, 
 wherein the laser beam is emitted from a light source and is irradiated on the surface of the glass sheet to form an irradiation area of the laser beam on the surface, and the laser beam that has been transmitted through the surface of the glass sheet is irradiated on the back face of the glass sheet to form an irradiation area of the laser beam on the back face; and 
 wherein in a case where each irradiation area includes a peak position of a power density of the laser beam, each irradiation area is arranged to have an asymmetrical power density distribution that is asymmetrical with respect to a reference line that passes through the peak position of the irradiation area and is parallel to a moving direction of the peak position, and in a case where each irradiation area does not include a peak position of a power density of the laser beam, each irradiation area is arranged to have an asymmetrical shape that is asymmetrical with respect to a reference line that passes through a centroid position of the irradiation area and is parallel to a moving direction of the centroid position. 
 
     
     
       2. The glass sheet processing method according to  claim 1 , wherein
 a product (α×M) of an absorption coefficient (α) (cm −1 ) of the glass sheet with respect to the laser beam and a moving distance (M) (cm) of the laser beam moving from the surface to the back face of the glass sheet is greater than 0 and is less than or equal to 3.0. 
 
     
     
       3. The glass sheet processing method according to  claim 1 , wherein
 the irradiation areas of the laser beam on the surface and the back face of the glass sheet are formed by shielding a part of a light flux of the laser beam, and irradiating a remainder of the light flux of the laser beam on the glass sheet. 
 
     
     
       4. The glass sheet processing method according to  claim 1 , wherein
 the laser beam emitted from the light source is focused by a focus lens and irradiated on the glass sheet, and the irradiation areas of the laser beam on the surface and the back face of the glass sheet are formed by arranging an optical axis of the focus lens and an optical axis of the laser beam entering the focus lens to be shifted from each other. 
 
     
     
       5. The glass sheet processing method according to  claim 1 , wherein
 each of the irradiation areas of the laser beam on the surface and the back face of the glass sheet is arranged into an ellipse shape having a minor axis or a major axis that is diagonal with respect to a moving direction. 
 
     
     
       6. The glass sheet processing method according to  claim 1 , wherein a wavelength of the laser beam is within a range of from 250 nm to 5000 nm. 
     
     
       7. The glass sheet processing method according to  claim 1 , further comprising:
 irradiating a heating light beam for heating the glass sheet at an irradiating position of the laser beam, and moving an irradiating position of the heating light beam with respect to the glass sheet along with the irradiating position of the laser beam with respect to the glass sheet. 
 
     
     
       8. The glass sheet processing method according to  claim 2 , wherein the irradiation areas of the laser beam on the surface and the back face of the glass sheet are formed by shielding a part of a light flux of the laser beam, and irradiating a remainder of the light flux of the laser beam on the glass sheet. 
     
     
       9. The glass sheet processing method according to  claim 2 , wherein the laser beam emitted from the light source is focused by a focus lens and irradiated on the glass sheet, and the irradiation areas of the laser beam on the surface and the back face of the glass sheet are formed by arranging an optical axis of the focus lens and an optical axis of the laser beam entering the focus lens to be shifted from each other. 
     
     
       10. A glass sheet processing apparatus, comprising:
 a support that supports a glass sheet; 
 a light source that emits a laser beam to be transmitted through the glass sheet from a surface to a back face of the glass sheet that is supported by the support; 
 an optical device comprising a lens and configured to irradiate the laser beam emitted from the light source on the glass sheet that is supported by the support; 
 an irradiating position moving device configured to move the support, the light source and the optical device, or the support, the light source and the optical device such that an irradiating position of the laser beam is moved with respect to the glass sheet; and 
 a control device comprising circuitry implementing a control program configured to control the light source, the optical device and the irradiating position moving device such that the optical device forms an irradiation area of the laser beam on the surface of the glass sheet by irradiating the laser beam emitted from the light source on the surface, and forms an irradiation area of the laser beam on the back face of the glass sheet by irradiating the laser beam that has been transmitted through the surface on the back face of the glass sheet, that the irradiating position moving device moves the irradiating position of the laser beam with respect to the glass sheet, and that a cleavage is formed in the glass sheet with thermal stress that is generated by irradiating the laser beam, 
 wherein the circuitry of the control device is configured to control the light source, the optical device and the irradiating position moving device such that in a case where each irradiation area includes a peak position of a power density of the laser beam, each irradiation is arranged to have an asymmetrical power density distribution that is asymmetrical with respect to a reference line that passes through the peak position of the irradiation area and is parallel to a moving direction of the peak position, and that in a case where each irradiation area does not include a peak position of a power density of the laser beam, each irradiation area is arranged to have an asymmetrical shape that is asymmetrical with respect to a reference line that passes through a centroid position of the irradiation area and is parallel to a moving direction of the centroid position. 
 
     
     
       11. The glass sheet processing apparatus according to  claim 10 , wherein the optical device includes a light shielding device configured to shield a part of a light flux of the laser beam emitted from the light source. 
     
     
       12. The glass sheet processing apparatus according to  claim 11 , wherein the light shielding device of the optical device comprises a light shielding plate configured to shield a part of a light flux of the laser beam emitted from the light source. 
     
     
       13. The glass sheet processing apparatus according to  claim 11 , wherein the light shielding device of the optical device comprises a light shielding film configured to shield a part of a light flux of the laser beam emitted from the light source. 
     
     
       14. The glass sheet processing apparatus according to  claim 10 , wherein the lens of the optical device comprises a focus lens that focuses the laser beam emitted from the light source, and an optical axis of the laser beam entering the focus lens and an optical axis of the focus lens are shifted from each other. 
     
     
       15. The glass sheet processing apparatus according to  claim 14 , further comprising:
 an optical axis position adjusting device configured to adjust a position of the optical axis of the focus lens with respect to the optical axis of the laser beam entering the focus lens. 
 
     
     
       16. The glass sheet processing apparatus according to  claim 10 , wherein the lens of the optical device comprises a cylindrical lens that focuses the laser beam emitted from the light source in a predetermined direction, and the optical device is configured to form the irradiation area of the laser beam that has an ellipse shape with a minor axis that is diagonal to a moving direction on each of the surface and the back face of the glass sheet that is supported by the support. 
     
     
       17. The glass sheet processing apparatus according to  claim 10 , further comprising:
 a focusing position adjusting device configured to adjust a focusing position of the laser beam with respect to the glass sheet that is supported by the support. 
 
     
     
       18. The glass sheet processing apparatus according to  claim 10 , wherein the light source emits the laser beam having a wavelength within a range of from 250 nm to 5000 nm. 
     
     
       19. The glass sheet processing apparatus according to  claim 10 , further comprising:
 a heating light source that emits a heating light beam for heating the glass sheet that is supported by the support, 
 wherein the irradiating position moving device is configured to move an irradiating position of the heating light beam with respect to the glass sheet along with the irradiation position of the laser beam with respect to the glass sheet. 
 
     
     
       20. The glass sheet processing apparatus according to  claim 10 , wherein the lens of the optical device comprises a plurality of cylindrical lenses that focus the laser beam emitted from the light source in a predetermined direction, and the optical device is configured to form the irradiation area of the laser beam that has an ellipse shape with a minor axis that is diagonal to a moving direction on each of the surface and the back face of the glass sheet that is supported by the support.